Scientists have developed an efficient, cheap way to vaccinate birds against avian influenza and possibly prevent the spread of the deadly H5N1 strain to humans. They have devised a method of combining avian flu vaccine with a vaccine already widely used against another very common bird virus.

With the H5N1 virus spreading among birds globally, American and German biologists working independently of each other have come up with the same approach to reducing the threat to people.

Using genetic engineering, they inserted genes from a bird flu virus into a second avian virus called Newcastle disease, for which a vaccine already exists. The combination virus that resulted from this laboratory experiment, when used in a vaccine, protected chickens against both diseases.

The bird flu viruses the two groups used were not the H5N1 strain that many fear could jump to humans and cause a deadly global pandemic. But the leader of the U.S. research team, microbiologist Peter Palese of the Mount Sinai School of Medicine in New York, says the experiments show in principle that the same approach could work against H5N1 in birds. "Clearly, the principle here is that we make a dual vaccine against both Newcastle disease virus as well as avian influenza and take advantage of the fact that every chicken already is vaccinated against Newcastle diseas," he said.

Newcastle disease vaccinations typically are sprayed into chicken coops or added to the birds' drinking water, quick and inexpensive methods of inoculation. Palese says his study and the one from Germany prove it is possible to design effective multi-disease vaccines that can be administered so cheaply to birds and at the same time cut the threat of avian flu to people. "So it would prevent the spread of avian influenza in chickens and poultry, which would reduce the danger that it would jump into humans," he said.

The German researchers, from the Friedrich Loeffler Institute, believe the combination vaccine approach could work with people as well as poultry. Although they did not specify how, presumably an annual flu virus could be combined with the H5N1 strain to produce a dual human vaccine if H5N1 ever mutates to transmit from person to person.

But infectious diseases physician William Schaffner of the Vanderbilt University School of Medicine in Nashville says the notion is premature. "At the moment, we are just developing pandemic influenza vaccines, so the optimal way to use those vaccines has not yet been established. So thinking about a strategy how they are going to be used, whether introduced into the routine [flu shot] or kept off to the side, is a little in advance of where we are. Nonetheless, you can be sure that those kinds of conversations in advisory committees have already occurred and no decisions have been made about that," he said.

The findings about a combination Newcastle disease and bird flu vaccine appear in the Proceedings of the (U.S.) National Academy of Sciences.